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Kemah, Texas
Watts Up! Marine Services has gone offshore and no longer provides local service. I have left this blog in tact for those that might find the information useful. I still monitor questions but only when internet is available.

Thanks for checking out our blog.

Tuesday, January 18, 2011

RCDs - How do we protect an entire circuit?

In conjunction with the previous blog posts, I wanted to answer a question that was raised; How do I protect my outlet circuits without having to change my current outlets?  Many boats have special cover plates made of teak, replacing the outlet to go to GFCI would require replacement of the cover plate and change the look of the boat.  RCDs are the solution to this problem.

Residual Current Devices (RCDs) respond to leakage of electrical current outside of the intended circuit path. When the RCD function is combined with overload and short circuit protection, the device is often referred to as an RCBO. A device that trips on leakages of nominally 5mA, and meets certain standards, is called a Ground Fault Circuit Interrupter (GFCI). A device meeting the same standards but with a trip level of 30mA is called an Electrical Leakage Circuit Interrupter (ELCI). The device to the right provides GFCI or ELCI functions and circuit protection in panel mounted breakers.  RCDs come in various sizes from 15 amp to 30 or 50 amp and can be used with 120 or 240 volt systems.  Make note, the size of the RCD can vary and the spaces that will be consumed in your electrical panel will increase with the size of the RCD.  As an example, a single circuit RCD will fill two positions in your electrical panel.

RCDs operate just like the GFCI you would find in your home or boat, they simply will protect the entire circuit to include the wiring that runs throughout your boat.  This is very important on a boat due to the flex and vibration that are an everyday occurrence, that will eventually take a toll on the the  electrical wiring.  Wire chafe is often found when removing old wiring, this chafe produced from wiring passing through bulkheads or under metal objects.  

In most cases, RCDs can replace the existing main A/C breaker (used as an ELCI), an individual circuit breaker or be added to an existing circuit depending on the existing circuitry.  It becomes an inexpensive solution that can be added to any boat.

To summarize the last couple blog posts, ELCIs will cover an entire boat, RCDs can protect an entire boat or each individual circuit and GFCIs offer protection to the individual outlet or string of outlets (if connected properly).  I hope that this sheds some light on electrical safety devices that can protect our boats and crew.

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